[Harry Bonar]

Dear Sir:
Your muzzle-loader is mis-crowned.
Cut the bbl back to get rid of this! Then get the muzzle square with a square. Make a hard wooden rod to fit bore and mount a cutter in it and crown equally.
Another simpler way is to use a large countersink (sharp) in your drill with about three thickneses of denim in between cutter and bbl. - turn slowly and then use grinding compound on a 60 degree point till even and smooth - you can do this.
Harry B.
Your trouble isn't the lands in bbl. - it's the crowning job.